1. Field of Invention
This invention relates to a method of diagnosing cancer and more specifically, for detecting premalignant cells.
2. Background
Lung cancer is the leading cause of cancer death in both men and women in the United States, accounting for an estimate 160,000 deaths per year. While male incidence is beginning to fall, female lung cancer incidence is increasing with a predominance of peripheral carcinomas (adenocarcinoma). Screening for frankly malignant lung cancer cells exfoliated from the airway epithelium has not resulted in frequent early-stage lung cancer detection and cure. Several lung cancer detection trials showed no reduction in lung cancer mortality among high-risk cohorts of smokers screened with sputum cytology and radiographic techniques compared with radiographic screening alone. These studies concluded that sputum cytopathology, while highly specific, is not sufficiently sensitive for lung cancer screening.
Larger airway epithelial lesions of sufficient size to alter radiographic contrast may be detected by new imaging technology, such as low-does multi-slice helical computerized tomography (CT) scans. Helical CT has been able to detect peripherally located nodules, especially those less than 1-2 cm. Preliminary results of helical CT screening at the H. Lee Moffitt Cancer Center and Research Institute at the University of South Florida have shown that at least 50% of CT-detected lung cancers are early-stage, potentially curable peripheral adenocarcinomas. However, 90% of CT-detected lesions are not cancerous (false positives).
Traditionally, molecular analysis has been performed on biopsies of whole tissue. Cellular heterogeneity of tissue specimens has confounded assessment of analyte levels of specific cell types. Laser capture microdissection (LCM) technology can now collect homogeneous populations of intact cells from solid tissue sections and cell smears for molecular analysis. Cells can be collected based on either morphology or immunohistologic features. LCM enables the user to procure pure cells from stained heterogeneous tissue under direct high-power microscopic visualization. The cells of interest are transferred to a polymer film that is activated by laser pulses. The exact morphology of the procured cells (with intact DNA, RNA, and proteins) is retained and held on the transfer film. Direct visualization of the captured cells, with their histology intact assures that the correct population of cells is selected. The ability of LCM to procure homogeneous cell subpopulations of normal, premalignant, and malignant cell types has had a significant impact on genomics and proteomics cancer research.
Significant technological advances in protein chemistry in the last two decades have established mass spectrometry as an indispensable tool for protein study, including discovery, identification (peptide mapping, sequencing), and structural characterization. Ciphergen Biosystems, Inc. (Fremont, Calif.) has developed ProteinChip® technology that utilizes surface enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS) to facilitate protein profiling of complex biological mixtures. References relating to the SELDI-TOF MS technology include U.S. Pat. No. 6,294,790 entitled “Secondary ion generator detector for time-of-flight mass spectrometry”; U.S. Patent Application No. 20010014461A1 entitled “Retentate chromatography and protein chip arrays with applications in biology and medicine”; U.S. Patent Application No. 20020060290A1 entitled “Method for analysis of analytes by mass spectrometry”; U.S. Patent Application No. 20020137106A1 entitled “Detection of biological pathway components”; U.S. Patent Application No. 20020138208A1 entitled “Method for analyzing mass spectra”; U.S. Patent Application No. 20020142343A1 entitled “Retentate chromatography and protein chip arrays with applications in biology”; U.S. Patent Application No. 20020155509A1 entitled “Retentate chromatography and protein chip arrays with applications in biology”; U.S. Patent Application No. 20020177242A1 entitled “Retentate chromatography and protein chip arrays with applications in biology and medicine”; U.S. Patent Application No. 20020182649A1 entitled “Methods for protein identification, characterization and sequencing by tandem mass spectrometry”; U.S. Patent Application No. 20030008412A1 entitled “Plate alignment and sample transfer indicia for a multiwell multiplate stack and method for processing biological/chemical samples using the same”; U.S. Patent Application Nos. 20030017464A1 and 20030032043A1 both entitled “Latex based adsorbent chip”; and U.S. Patent Application No. 20030054367A1 entitled “Method for correlating gene expression profiles with protein expression profiles” all assigned to Ciphergen Biosystems, Inc. and all incorporated herein by reference.
The ProteinChip® technology advanced by Ciphergen Biosystems utilizes biochip arrays to capture individual proteins or groups of proteins with common biochemical properties such as hydrophobicity or charge from complex mixtures. These retained proteins are subsequently resolved directly by time-of-flight mass spectrometry. It is fast, sensitive and scalable for high-throughput sample processing. These characteristics make SELDI technology suitable for the studies of cancer development from premalignant lesions when minimal, multiple protein changes may have pathodiagnostic significance.